The invention relates to a method for the production of synthetic blood vessel prostheses and a synthetic blood vessel prosthesis produced by the method of the invention.
Blood vessel prostheses are tubes or pipes which are inserted as synthetic sections of arteries and veins in the medical practice for both human and animal medicine. Thus, blood vessel prostheses serve surgical purposes.
Synthetic blood vessel prostheses are known which are manufactured as seamless, accordion-pleated, knitted or woven tubes of yarn. The pleating of these tubes is intended to prevent kinking under heavy bending stress. Should they kink, the passage of blood through them would be greatly throttled or even entirely blocked. Such pleating, however, may disappear after implantation, either in the course of growing in or subsequently as well, to such an extent that the danger of kinking arises. Furthermore, the pleating causes turbulences in the flowing blood, which can be very disadvantageous. Also, the yarn forming the weave or knitting may be damaged by pleating, which results in weakened blood vessel prostheses. These blood vessel prostheses have the further property, which is often disadvantageous, that they are always substantially inelastic radially, or become inelastic in the course of time as a result of unavoidable ingrowth of connective tissue, the former being the case with woven blood vessel prostheses from the outset and the latter applying to knitted blood vessel prostheses. This is a property which natural blood vessels do not have, since natural blood-vessels expand when the blood pressure rises and retract in an elastic manner when the blood pressure goes down.
Knitted blood vessel prostheses also have the further disadvantage that at the connection point with the adjacent natural blood vessel (either artery or vein), the seam which forms this connection of the blood vessel prosthesis with the natural blood vessel can lead to raveling of the synthetic knitted blood vessel prosthesis.
Synthetic blood vessel prostheses are also formed as microporous, radially inelastic and thus not elastically expansible, bendable tubes of polytetrafluorethylene (PTFE). These tubes do avoid the danger of kinking; however, the lack of radial expansibility is often disadvantageous. Also, the material of these tubes creeps and as a result they stretch irreversibly over a relatively long period of time; this causes the physiological flow relationships of the blood in such tubes to change, which is disadvantageous and undesirable.